Introduction: The diagnosis of heart failure in a patient carries a prognosis of 35-40% 1-year mortality. Among factors predicting mortality, hyponatremia has been associated with 2-3 fold increase in in-hospital and post discharge mortality. There is paucity of data from Indo-Asian population on outcomes of heart failure and factors predicting mortality.
Objectives: To compare 30-day mortality rate in heart failure patients with and without hyponatermia (serum sodium <136 and ≥136 mmol/L. respectively).
To compare these two groups for length of stay, rate of rehospitalization and functional status (NYHA criteria).
Materials and Methods: A prospective cohort study of 164 patients with heart failure was conducted. Patients were recruited from the emergency department of Aga Khan Univerity Hospital over a 6-month period. Patients with and without hyponatremia were followed for death, length of hospital stay, rehospitalization and functional status at 30 days. Data was analyzed using SPSS version 16.0 and a P-value of <0.05 was considered statistically.
Results: The average age was 64±13 years, and 55% of patients were male. Comorbids: 92% had Hypertension, 88% had Coronary Artery Disease, 62% had Diabetes Mellitus, 40% had Chronic Kidney disease.
Mortality This was 4% in patients with normal serum sodium and 10% in patients with hyponatremia.
Multivariate analysis: The odds of having sodium < 136mmol/l among those who died was 3.04 (95% CI 0.77-12.04) as compared to those who survived, though this was not statistically significant (p=0.113). The odds of having hyponatremia among those who had good NYHA functional class was 0.16 (CI 0.07-0.34) compared to those with poor NYHA functional class (p<0.001). The odds of having hyponatremia among those who were re-hospitalized was 0.2 (CI 0.05-0.78) times that of those who were not re-hospitalized (p=0.021).
Conclusion: Hyponatremia (serum sodium <136mmol/L) in heart fauilure was associated with a tendency towards higher mortality, though not statistically significant. Hyponatremia was significantly associated with lower re-hospitalization rate and poor NYHA functional class. A study with larger sample size or longer follow up period may identify significance of hyponatremia as a predictor of mortality, hence relevant interventions can be targeted to improve outcome.